Helicopters, in general, have the same basic configuration or layout. For instance, a typical helicopter will have a cabin section which is used to transport people, cargo or both. In addition, the helicopter will have an engine compartment which is located typically above and to the rear of the cabin section. The engine compartment will house two primary components, at least one engine and a rotor transmission with a corresponding transmission housing.
Both the engine and the rotor transmission contain numerous fluids, such as petroleum-based lubricants, that are critical to the operation of the engine and the transmission. These fluids inevitably leak from various locations in the engine and the transmission during both the operation and storage of the helicopter. Because the engine compartment is generally oriented above the cabin section, any leaking fluids eventually seep or drip into the cabin section, unless proper sealing mechanisms are in place. The inflow of these leaking fluids spoil, stain or damage the cabin's interior materials such as seat covers and acoustic linings. In addition, the leaking fluids can severely damage or destroy sensitive electronic equipment that may be placed in the cabin section of, for instance, a BLACKHAWK.TM. helicopter.
Moreover, the exterior of the helicopter around the engine and transmission compartment is not completely watertight, allowing water to leak from these areas into the cabin with similar adverse effects.
During routine inspection and maintenance it is necessary to have ready access to the engine and the rotor transmission. Such access is required to check critical fluid levels, to replace worn or damaged parts, or to adjust mechanical systems. Typically, various access panels in or around the engine compartment provide the requisite openings to achieve ready access to the engine and the rotor transmission. In some helicopters, such as the BLACKHAWK.TM. helicopter, a forged airframe structure forms an access opening which is located below the rotor transmission housing and above the cabin section. The opening is thus accessible through the cabin's ceiling. This access opening, however, must be sealed by a cover against the inevitable oil and fluid drippings which the engine and the rotor transmission will produce, as well as against water leakage.
The access opening below the engine compartment in the BLACKHAWK.TM. helicopter is defined by both the aircraft structural forgings and a flexible or yieldable downwardly-turned skirt which is riveted onto the helicopter's forged structure. The skirt is thin and many times more flexible relative to the helicopter's forged structure.
Prior drip pan designs attached a covering plate directly to the flexible skirt with a hollow seal sandwiched therebetween. One hollow seal used in prior designs resembled the flexible, hollow door seals used around car doors or refrigerator doors. However, the skirt contains surface aberrations, such as the protruding rivet heads from the rivets securing the skirt to the forged helicopter structure. When the seal engaged both the skirt and the rivet heads, it could be upset enough so that leakage occurred. Accordingly, the hollow seal traversing these aberrations while sandwiched between the skirt and the covering plate is unable to provide a suitable, consistent, long-term fluid seal. Moreover, flexing of the flexible skirt could also cause leakage.
Also, the geometry of the cover cannot be such that it protrudes significantly into the interior of the cabin section. Headroom in the cabin section typically is limited and any additional protrusion from the ceiling of the cabin section is undesirable. In addition, because weight is critical to the operation of any aircraft, heavy cover constructions are undesirable.
Accordingly, one objective of this invention is to provide an improved cover and seal for the interior access opening of helicopters such as the BLACKHAWK.TM. helicopter and those of similar structure.
Another object of this invention is to provide a drip pan that will effectively and consistently seal fluid from passage from an engine or transmission compartment to a cabin section of a helicopter.
Another object of this invention is to provide a drip pan which permits quick access to the engine or transmission compartment of a helicopter without requiring modification to the existing aircraft structure.
Another objective of the invention is to more effectively seal a drip pan to the skirt defining a transmission access opening in a BLACKHAWK.TM. helicopter.
Still another object of this invention is to provide a drip pan that can be attached to the existing structure of a BLACKHAWK.TM. helicopter without modification of the existing airframe structure and with minimal intrusion into the helicopter's cabin section.